A ball is tossed upward with a speed of 2 m/s from 1.5 m above the ground. How long will it take the ball to reach the ground? (This problem is tricky, so you may have to think outside of the box)

The illuminance of a surface varies inversely with the square of its distance from the light source. if the illuminance of a surface is 120 lumens per square meter when its distance from a certain light source is 6 meters, by how many meters should the distance of the surface from the source be increased to reduce its illuminance to 30 lumens per square meter?